The invention concerns a system for evaluating vehicle, drive and operation parameters.
The desire for greater economy in motor vehicles with very good driveability demands, better coordination in the characteristic field of a prime mover and the vehicle operating conditions over the most favorable operating ranges. This is achieved with a multi-step or continuously variable transmission having a large speed ratio range. To be able to utilize the advantages, the transmission has to be optimally gear shifted or adjusted, which imposes high demands on the driver. If the continuously variable transmission is regarded as a transmission with several unlimited steps, considerations that apply to multi-step transmissions can, generally, be similarly transferred to a continuously variable transmission. Therefore, for the sake of simplicity, reference will hereinafter is particularly made to multi-step transmissions using the terminology adapted thereto.
In order to unburden the driver and increase comfort in driving, there is increasingly offered vehicles which have a fully automated train consisting of an engine, a starting element, such as a clutch and/or a converter, a gear with different speed ratios and a drive axle with wheels.
Part of the automation consists in selecting, for the respective operating state of the vehicle, a favorable speed ratio and determining the correct gear shift moment. At the same time, it must be taken into consideration that economy and driving comfort must not be impaired by too frequent gear shifts.
Already known are automatically shifting step-changing gears for motor vehicles which automatically shifted within the range of the gears available primarily depending on the number of revolutions and which are proportional to the driving speed and on load states, such as the position of the accelerator pedal or throttle pedal when idling, part load, full load or kick-down. In order to reduce the number of gear shifts, the driver can eliminate from the gear shift sequence, via a selector switch, gears in the upper or lower range, e.g. when mountain driving or in winter operation.
From DE 32 47 658 A is known, by a separate selector lever, to exclude from the automatic gear shift the number of gears not only in the upper range but also simultaneously in the lower range. This is especially favorable when idling or traveling with part load. Of course, the reduced number of automatically shiftable gears results in poor adaptation to the economic operating range of the engine.
It is further known from ATZ 85 (1983) 6, p. 393 ff that a electronic microprocessor system can determine the gear to engage according to a predetermined computing program. In one gear shift characteristic field, if an upshift or downshift characteristic line is reached, the electronic system triggers a corresponding gear shift operation. During the gear shift operation, the torque of the engine becomes reduced in order less to load the friction elements and improve driving comfort. For different driving situations, several programs are provided which have different gear shift characteristic fields. It is possible here to automatically change between the individual gear shift characteristic fields. It is also possible to adapt the gear shift characteristic lines according to desired operation parameters.
For commercial motor vehicles, multi-step mechanical transmissions are often used which are shifted with traction interruption. EP 0 255 519 B1 has disclosed a control device for automatic gear shifting of multi-gear step changing transmissions in which the gear shift points are established depending on the vehicle speed, the momentary requirement (throttle pedal position) and the acceleration determined from the number of revolutions of the gear output shaft. The acceleration is divided in six ranges, namely, a high deceleration, a low deceleration, a constant drive, a low acceleration, a medium acceleration and a high acceleration. Deceleration is computationally considered as negative acceleration.
Besides, the throttle pedal position is divided in three ranges, namely, an empty gas range, a medium position and a full gas range. With each range of the throttle pedal position is associated an acceleration range so that under said premisses eighteen gear shift points result. The gear shift conditions for the gear shift points are contained in tables wherein the values are empirically or computationally determined. According to the number of travel programs used, several tables are needed. The characteristic fields and tables required for the gear shift must be adapted to each type of vehicle and drive train. This involves considerable expenditure, since more than 3000 data must be considered. Besides, changes between the many unevenly stepped gear shift conditions are critical, since interactions can easily be generated which act unfavorably on the driveability of the vehicle.